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Biomedical subjects

R Lock

Publications and source records attributed to R Lock.

16 recordsLinked to original sources
PubMed1997

Na+ and Ca2+ homeostatic mechanisms in isolated chloride cells of the teleost Oreochromis mossambicus analysed by confocal laser scanning microscopy

Chloride cells (CCs; recognised by the vital mitochondrial stain DASPEI) and pavement cells (PCs) isolated from tilapia opercular epithelium were adhered to Cell-Tak-coated glass coverslips and loaded with fluorescent probes for the measurement of intracellular concentrations of Na+ or Ca2+. Basal levels of cytosolic Na+ and Ca2+ ranged from 6.4 to 16.5 mmol l-1 and from 76 to 110 nmol l-1, respectively, and did not differ between CCs and PCs. In CCs, inhibition of Na+/K+-ATPase by ouabain or Cu2+ increased intracellular [Na+]. Replacing extracellular Na+ with N-methyl-d-glucamine+ led to a rise in cytosolic [Ca2+] that was dependent on the extracellular [Ca2+], indicating that a Na+/Ca2+ exchanger was operating in reverse mode (importing Ca2+). The forward mode of this exchanger could be demonstrated by inhibition with bepridil. The CC has various pathways for passive Na+ influx: a tetrodotoxin-sensitive pathway, an amiloride-sensitive pathway and other as yet unidentified pathways.

Journal Article↗
PubMed1996

Antibody response in bronchoalveolar lavage and serum of rats after aerosol immunization of the airways with a well-adhering and a poorly adhering strain of Streptococcus pneumoniae.

This study describes the antibody response to two bacterial antigens, pneumolysin toxoid (PL) and purified pneumococcal capsular polysaccharide (PPS) 19F, in bronchoalveolar lavage (BAL) and in serum in rats after aerosol immunization with whole killed Streptococcus pneumoniae. To study the importance of bacterial adherence for antibody formation, one well-adhering and one poorly adhering strain of S. pneumoniae was used. The results show local specific anti-PPS 19F IgA, IgM and IgG antibody activities after aerosol immunization. Anti-PL antibody activity in all three immunoglobulin classes was found, although the anti-PL activity was lower than the anti-PPS 19F antibody activity. The IgA anti-PPS 19F antibody activity in BAL after immunization with the well-adhering strain was higher than with the poorly adhering strain. We conclude that aerosol immunization with S. pneumoniae induces a local, specific antibody production in the lung of the rat.

Aerosols↗
PubMed1995

Branchial chloride cells in larvae and juveniles of freshwater tilapia Oreochromis mossambicus

Branchial chloride cells in the developing larvae and juveniles of freshwater tilapia, Oreochromis mossambicus, were identified and the membrane Na+/K+-ATPase was localized in situ through binding of the fluorescent dye anthroylouabain. After co-labelling of the cells with the fluorescent probes DASPMI and Con-A-FITC, the mitochondria and apical crypt in the same chloride cells were visualized using confocal laser scanning microscopy. The high density of apical crypts indicated that many chloride cells were functional. The density of branchial chloride cells in larvae 10 days after hatching was approximately 6000 mm-2. An extremely high Na+/K+-ATPase specific activity of approximately 1500 µmol Pi h-1 mg-1 was measured in the gills 10 days after hatching. With the development of secondary lamellae and hence an increase in the amount of branchial epithelial protein, a concomitant decrease in the specific activity of the enzyme in the gill tissues was observed. Total Na+/K+-ATPase activity increased markedly in the early life stages. Our data indicate that in larval stages of fish the gills form a functional ionoregulatory organ before they start functioning as a gas-exchange organ.

Journal Article↗
PubMed1992

Phagocyte killing of Campylobacter jejuni in relation to oxidative activation.

When studying the interaction between Campylobacter jejuni and human neutrophils, we found that four different clinical isolates showed a great variability in this association. Also the ability to induce neutrophil production of oxidative metabolites, measured as chemiluminescence (CL), differed between the strains. Surprisingly, strain 1, which showed weak interaction with neutrophils and high resistance to killing, induced the highest CL response. All strains evoked an intracellular CL response, and three strains also gave rise to an extracellular response. This extracellular release of toxic oxygen species might contribute to the local tissue damage during infection. There was no clear correlation between association, killing and oxidative response. However, one strain that only evoked an intracellular generation of oxygen metabolites also showed the highest sensitivity to killing. Phagocytosis was increased up to ten times after opsonization with normal human serum. The intracellular CL production increased several fold, whereas the extracellular generation of oxygen species disappeared or was considerably decreased after opsonization. These results indicate that complement-opsonized C. jejuni are phagocytosed and readily attacked by the oxidative defence system within the phagosome.

Campylobacter jejuni↗
PubMed1991

Post-arthroscopic pulmonary edema in two healthy teenage athletes.

Outpatient arthroscopic knee surgery carries with it certain risk factors similar to those accompanying other major knee procedures. These risks may be related to the complexity of the procedure, exposure to anesthesia, or risk factors from previous medical history. Two cases of acute pulmonary edema following arthroscopic knee surgery in otherwise healthy teenage athletes are presented. Both patients developed acute respiratory distress in the recovery room after uneventful arthroscopic knee surgery. The patients in both cases recovered and were able to return to sporting activity with no sequelae. The similarities in both cases prompted a retrospective investigation of the events from the induction of general anesthesia to the admission of the patients to the intensive care unit. Several possible causes of acute post-operative pulmonary edema include fluid overload, cardiac arrhythmia, respiratory depression, systemic drug reaction and sickle cell trait or disease. Outpatient arthroscopy still remains the procedure of choice for meniscal pathology of the knee, but the surgeon and the anesthesia personnel must be aware of and prepared for pulmonary complications that may arise in the immediate post-operative period.

Acute Disease↗
PubMed1990

Neutrophil killing of two type 1 fimbria-bearing Escherichia coli strains: dependence on respiratory burst activation.

The production of reactive oxygen metabolites by neutrophils is thought to play a key role in host defense against invading microorganisms. In this study, the generation of oxygen metabolites induced by two uropathogenic Escherichia coli strains, ABU2 and PN7, and their subsequent killing in neutrophils were investigated. Both strains were grown to promote type 1 (mannose-sensitive) fimbria formation, but they differ with respect to other surface structures. When interacting with human neutrophils, the ABU2 bacteria adhered to and were phagocytized by the neutrophils, whereas PN7 bacteria adhered to the neutrophils but resisted phagocytosis. Both strains induced a pronounced neutrophil chemiluminescence response. However, when the intracellular and extracellular parts of the oxidative response were separated, we found that the predominant part of the response was of intracellular origin with the ABU2 bacteria as prey, whereas a large fraction of the response induced by the PN7 bacteria was extracellular. The general opinion is that production of reactive oxygen metabolites should be intraphagosomal to minimize the tissue-damaging effects of the metabolites and to optimize their bactericidal effects. However, since the surface-adherent bacteria (the PN7 cells) are killed in an aerobic but not an anaerobic milieu, whereas the ingested bacteria (the ABU2 cells) are killed in both aerobic and anaerobic milieu, we propose that extracellularly generated oxygen metabolites are of importance in killing E. coli strains that can resist neutrophil engulfment.

Aerobiosis↗
PubMed1989

Localization of the luminol-dependent chemiluminescence reaction in human granulocytes.

The granulocyte luminol-dependent chemiluminescence (CL) reaction is linked to the enzyme myeloperoxidase reacting with products of the respiratory burst activation. The results presented in this paper, show that the light generated in granulocytes originate both from intracellular and extracellular reactions; however, depending on the stimulus used the one or the other will dominate the activity measured. Furthermore, lysosomal fusion is proposed to be required for the intracellular CL reaction.

Adult↗
PubMed1988

Analysis of horseradish peroxidase-amplified chemiluminescence produced by human neutrophils reveals a role for the superoxide anion in the light emitting reaction.

When polymorphonuclear leukocytes and soluble or particulate matter interact, the cells produce chemiluminescence, which is linked to activation of the oxidative metabolism of the cells. A luminol chemiluminescence assay in which the reaction mixture contains a relatively large amount of horseradish peroxidase combined with sodium azide has been proposed to quantitate H2O2 produced by human neutrophils during the respiratory burst (M.P. Wymann, V. von Tscharner, D. A. Deranleau, and M. Baggiolini (1987) Anal. Biochem. 165, 371-378). We found, when comparing the response to concanavalin A and a formylated peptide (formylmethionyl-leucyl-phenylalanine), that neutrophils produce H2O2 that is not detected as chemiluminescence by the horseradish peroxidase-azide-luminol system. Furthermore, the horseradish peroxidase-amplified chemiluminescence response obtained from granule-depleted neutrophil cytoplasts is inhibited by superoxide dismutase, an O2- scavanger. Based on these results, we question the specificity of the described technique for H2O2. The usefulness of the technique in the determining the extracellular and intracellular production of oxidative metabolites is discussed.

Catalase↗
PubMed1988

Reduced redox potential during growth of some gram-negative bacteria. Effect on the biochemical and physicochemical surface properties and phagocytosis by polymorphonuclear leukocytes.

When cultivated at reduced redox potential the physico-chemical surface properties were altered in strains of E. coli, Salmonella and Yersinia bacteria. In particular, strains which showed hydrophilic surface properties under normal aerobic cultivation became more hydrophobic when exposed to anaerobic conditions (e.g. E. coli K12, E. coli K12D21, E. coli K12D22, S. minnesota S99, S. typhimurium 395MS, S. braenderup 2828 and Yersinia enterocolitica). Moreover, there were qualitative as well as quantitative differences in the protein profiles of whole bacterial lysates and membrane preparations analysed in SDS-PAGE. There were no qualitative differences in the lipopolysaccharide (LPS) bands. However, when E. coli K12D22 were cultivated aerobically, remarkably more high molecular temperature-sensitive (70 degrees C for 45 min) carbohydrate material was produced (weight about 360 KD and 660 KD). Interaction between polymorphonuclear leukocytes (PMNL) and the E. coli K12D22 strain, measured as chemiluminescence, showed that the anaerobically cultivated bacteria induced a chemiluminescence that was mainly of intracellular origin, while the aerobically cultivated induced an extracellular response. Phagocytosis and killing-studies showed that only anaerobically-grown E. coli were effectively inactivated by the PMNL.

Aerobiosis↗
PubMed1988

The limitation of the human neutrophil chemiluminescence response by extracellular peroxidase is stimulus dependent: effect of added horse radish peroxidase on the response induced by both soluble and particulate stimuli.

When polymorphonuclear leukocytes (PMNL) interact with soluble and particulate stimuli, the cells increase their production of oxidative metabolites. This increased production can be measured as luminol amplified light emission or chemiluminescence (CL). The CL response of human PMNL has been investigated, and it was found that the formyl-methionyl-leucyl-phenylalanine (FMLP) and the phorbol myristate acetate (PMA) induced responses were limited by the amount of available peroxidase, whereas the ionomycin induced response was unaffected by the amount of extracellular peroxidase. A small increase in the response induced by the Salmonella typhimurium MR10 bacteria upon addition of peroxidase was also observed. The results indicate that stimuli inducing an intracellular response in PMNL are insensitive to the amount of extracellularly released peroxidase, whereas the response induced by stimuli also generating an extracellularly located production of oxidative metabolites are highly influenced by the amount of peroxidase available extracellularly. Furthermore, the extracellularly localized peroxidase dependency is reduced at higher luminol concentrations. The use of the luminol-amplified chemiluminescence technique in various types of scientific investigations is discussed.

Adult↗
PubMed1988

Characteristics of the granulocyte chemiluminescence reaction following an interaction between human neutrophils and Salmonella typhimurium bacteria.

The production of reactive oxygen metabolites by neutrophils is thought to play a key role in the host defence against invading microorganisms. The production of these oxidative metabolites can be measured as chemiluminescence. In this study, two strains of Salmonella typhimurium were used as stimuli, and the opsonin-independent CL response from neutrophils challenged with these bacteria was investigated. The strains used, S. typhimurium 395 MS and a rough (Rd Epi-2) mutant 395 MR10, differ with respect to physicochemical surface characteristics. When neutrophils were exposed to the phagocytic prey, only the MR10 bacteria induced a CL response. The response induced by the MS bacteria was less than 2% of that induced by MR10. In order to study the relation between intra and extracellularly generated CL, systems were used which selectively inhibit the intra and extracellular CL, respectively. Using these systems it was found that a predominant part of the response was of intracellular origin. When the neutrophils were treated with cytochalasin B (5 micrograms) before the addition of the bacteria, the CL response was reduced to around 37% of the value obtained from untreated cells, and the relation between the extra and the intracellular parts of the response was changed. The mechanism(s) and biological consequences of the extracellular and intracellular generation of oxygen metabolites, respectively, are discussed.

Cytochalasin B↗
PubMed1984

Premenstrual exacerbation of asthma.

Questionnaires and twice daily peak expiratory flow measurements were used to evaluate the effects of the menstrual cycle in asthmatic women. Forty per cent of women reported premenstrual deterioration in their symptoms and this was confirmed by peak flow recordings. No correlations were found between premenstrual exacerbation of asthma and symptoms of premenstrual tension, consumption of aspirin, use of the contraceptive pill, cycle length, or behaviour of asthma during pregnancy.

Adolescent↗
PubMed1983

Post-catheterisation urethral strictures. A clinical and experimental study.

Seventeen patients who developed urethral strictures following catheterisation have been studied; 14 of these (82%) were catheterised for standard monitoring purposes during and after major heart surgery, which was a coronary artery bypass graft (CABPG) in 12 cases. The possible aetiological mechanisms for the development of this complication are discussed. Animal experiments were designed and carried out to compare the effects of different catheter materials on the urethral mucosa. Silicone catheters provoked the least inflammation and rubber the most. A further experiment determined the flow rates through catheters of different sizes. From our results, we suggest that the careful insertion of a small silicone catheter, distally fixed, is least likely to induce stricture formation.

Adolescent↗
PubMedDate not supplied

Infusing a teacher preparation program in learning disabilities with assistive technology.

A recent trend in the fields of special education, rehabilitation, and technology is the development and implementation of assistive technology (AT) devices and services to assist individuals in compensating for disabilities and/or utilizing functional capabilities to meet environmental demands. AT devices and services have major implications for individuals with learning disabilities (LD) regarding life span issues, environmental and curricular accessibility, and compensatory strategies. Faculty members in higher education who are responsible for designing teacher preparation programs in LD must explore ways to structure curricula, methodologies, and practica to better prepare teachers to work with students who use AT devices to compensate for their specific learning disabilities. The purpose of this article is to describe curriculum design steps and barriers to and solutions for infusing LD teacher preparation programs with assistive technology.

Curriculum↗